The present invention relate to valves in general, and more particularly to improvements in valves of the type wherein a component is movable in the direction of fluid flow. Still more particularly, the invention relates to improvements in valves which can be utilized as shutoff valves and/or for regulation of fluid flow. Valves of the type to which the present invention pertains are also known as restrictors wherein the amount of restriction can be varied.
It is already known to install a piston-like valve element in the body of a valve and to provide actuating means for moving the valve element axially toward or away from a stationary valve seat in the body. The actuating means may be manipulated by hand, by remote control or automatically. In each instance, at least a portion of the actuating means must extend into the interior of the valve body in order to be coupled to the axially movable valve element. Reference may be had to German Pat. No. 473,538 which discloses a hollow cup-shaped valve element having a ring-shaped sealing member and being movable into and from engagement with an annular seat in the valve body. The means for actuating the valve element includes a shaft or spindle which is coaxial therewith and a bell crank lever having an inner arm which is articulately connected to the shaft, an outer arm which is accessible from without the valve body, and a median portion which is fulcrumed in the valve body.
A drawback of such conventional valves is that one or more portions of the actuating means for the axially movable valve element extend into the interior of the valve body. Such portions include bearings, pivot pins, guide means, parts of linkages and the like. Consequently, such portions of the actuating means are in permanent contact with the fluid. If the liquid is corrosive or contains one or more corrosive agents, it can shorten the useful life of the actuating means and/or necessitates frequent inspection, replacement or repairs. Moreover, and if the confined liquid is maintained at an elevated temperature, the external portion or portions of the actuating means must be thermally insulated from the internal portions so as to allow for manipulation by hand. Still further, the valve body must be provided with adequate seals to prevent leakage of fluid in regions where portions of the actuating means extend therethrough. This can present problems when the pressure of confined fluid is high. As a rule, the entire valve must be detached from the pipeline whenever a component part thereof necessitates inspection, replacement or repair.